Detective Dick Gumshoe is the only detective currently employed that Phoenix [Wright] has any contact with. Though well meaning, he's not the sharpest tool in the shed.
Personality: Gumshoe takes great pride in his work, and also in his "strong bond of trust" with the prosecutor's office. He's usually cheerful, is hardworking, and eager to please. But he also takes his job seriously, which causes conflict when he wants to help both sides of the case. Can sometimes be easily discouraged.
Misc Facts: Gumshoe LOVES steak lunches.
Gumshoe has two distinct styles of speech depending on which version you play. In the English, Gumshoe ends a lot of his sentences with "Pal." In the Japanese, Itonoko uses slang in which he slurs the ends of his sentences (i.e. "nan desu ka?" becomes "nansska?"). Listen for it in the TGS trailer.
The reason Gumshoe seems to be the only working detective through the series is because he uses his "powers of persuasion" to get himself assigned to many cases.
Friends and Family: Gumshoe has no known family members, but he's very loyal to Prosecutor Edgeworth.
Name Origin: English: "Dick" is obviously a reference to him being a "detective," and "Gumshoe," is a common slang for a PI.
Japanese: "Itonokogiri" roughly means, "a saw." The creator says he chose the name for its uniqueness. The name "Keisuke" was taken from a musician.
French: Comes from "detective."
Background: Not much about Gumshoe's back story is known, other than he became a detective roughly six months before the case of State vs Fawles.